1. Field of the Invention
The present invention relates generally to a substrate transporting and processing system and a cleaning system. More specifically, the invention relates to a substrate transporting and processing system and cleaning system for sequentially transporting substrates to be processed, such as semiconductor wafers and glass substrates for LCDs, to suitably process the substrates.
2. Description of the Prior Art
In general, in production processes in semiconductor fabrication systems, substrate transporting and processing systems are widely used for sequentially transporting substrates to be processed, such as semiconductor wafers and glass substrates for LCDs (each of which will be hereinafter referred to as a "wafer"), to a processing bath for storing therein a processing solution, such as a chemical and a rinse solution (a cleaning solution), or a dying section to carry out the processings, such as cleaning and drying, of the wafers.
In order to efficiently clean a plurality of wafers, e.g., 50 wafers, in such a substrate transporting and processing system, vertically arranged wafers are preferably transported into and from respective processing units.
In this type of processing system, a plurality of processing units and a cleaning unit of a transport means are typically arranged in a line between a container for housing therein unprocessed wafers, e.g., a supply section of a carrier, and a container for housing therein processed wafers, e.g., a discharge section of the carrier.
In recent years, with the miniaturization, super high integration and mass production of semiconductor devices, the diameter of the wafers has been increased from 8 inches to 12 inches.
However, since the size and weight of the wafers increase with the increase of the diameter of the wafers, if the vertically arranged wafers are transported from the supply section to the discharge section as the conventional manner, when the wafers are delivered between the supply and discharge sections and the processing section, there are problems in that the displacement of the wafers may occur and particles may be produced due to the movement of the wafers, so that the yield of products may be decreased.
In addition, with the increase of the diameter of the wafers, the size of the transport means and the respective processing units increases, so that there are problems in that the size of the whole system increases and the throughput decreases.
By the way, in processes for producing semiconductor devices, cleaning systems are used for removing particles and contamination, such as organic contamination, from the surface of semiconductor wafers (each of which will be hereinafter referred to as a "wafer"). Among the cleaning systems, in a wet cleaning system for immersing wafers in a cleaning solution in a processing bath, there is advantage in that particles adhered to the wafers can be effectively removed.
Typically, the wet cleaning system comprises an interface section, to which a cassette loaded with wafers is transferred, a cleaning section for cleaning and drying the wafers, and a transfer unit for transporting the cassette between the interface section and the cleaning section. The interface section has a transport gate. The cassette transported by an automatic guided vehicle (AGV) is transported into and from the cleaning system via the transport gate. The cleaning section includes a unloader for unloading the wafers from the cassette, various cleaning baths for cleaning the wafers, a drying bath for drying the wafers, and an loader for loading the wafers into the cassette. When the cassette is transferred to the interface section by means of a robot or the like, the cassette is transported into the cleaning section by means of the transfer unit. Then, the wafers are unloaded from the cassette by means of the unloader of the cleaning section. Then, e.g., 50 wafers housed in two cassettes are transported into the respective cleaning baths together to be batch cleaned using various liquids. Then, in the drying bath, the moisture on the surface of the wafers is removed using, e.g., isopropyl alcohol (IPA), simultaneously with volatilization of IPA.
The cleaning system having the above construction is generally located in a clean room having a high cleanliness. The interior of the clean room is maintained in a clean atmosphere wherein dust produced from human bodies and frictional sliding parts of machine, and impurities, such as gases and chemicals, are inhibited from being produced so that the amount of the dust and so forth is as small as possible. On the other hand, since various chemicals are used for cleaning and drying the wafers in the cleaning section of the wet cleaning system, there is a probability that the vapor of chemicals and the vapor of IPA used in the drying bath remain in the cleaning system. If the vapor leaks out of the cleaning system via the transport gate of the interface section, the interior of the clean room is contaminated.
Therefore, the interior of the cleaning system is maintained in an atmosphere of negative pressure, and the pressure inside the clean room is set to be higher than the pressure inside the cleaning system by, e.g., +0.38 mmHg, to prevent the atmosphere inside the cleaning system from leaking out via the transport gate of the interface section.
However, if there is a differential pressure between the cleaning room and the cleaning system, an airflow entering the interior of the cleaning system from the clean room via the transport gate of the interface section is formed. If particles, together with the airflow, enter the interior of the cleaning system, or if the arrow in the system is disturbed, there is a problem in that particles and mist are adhered again to the wafers, which have been cleaned. In addition, if the airflow enters the drying bath, which is drying the wafers using the IPA vapor, it is not possible to suitably supply the IPA vapor to the surfaces of the wafers, and there is a bad influence that water marks remain on the surfaces of the wafers.
On the other hand, in order to inhibit such an airflow from being produced, it has been attempted to provide a baffle board between the interface section and the cleaning section. However, if such a baffle board is provided, the wafers must bypass the baffle board when the wafers are transported between the interface section and the cleaning section, so that it is not possible to provide a straight transport path. Therefore, it takes a lot of time to transport the wafers, so that there are problems in that the tact time is increased and the throughput is decreased.